Method and device for time-synchronized relaying of signals

ABSTRACT

The invention relates to a method and device for the time-synchronised relaying of signals, whereby various signals from at least one signal source are relayed over various signal paths to at least one signal receiver, with time markers overlaid on the various signals. The delays occurring in the various signal paths are determined, a minimum total delay is calculated from the determined delays and information as to the minimal total delay is inserted in the various signals in the form of time-markers. A time-synchronous relaying of the signals is guaranteed in each signal path by means of an individual signal delay, the delay value of which corresponds to the difference between the minimal total delay and the delay caused by signal processing imposed on the signal in each signal path.

DESCRIPTION

[0001] The invention is concerned with a method and a device fortime-synchronous conduction of signals.

[0002] Such time-synchronous conduction of signals is of importance forexample for audio/video systems and for multichannel audio systems. Inthose cases, there is always the necessity to have signals, transferredfrom one or several signal sources to one or several signal sinksthrough various signal paths, be conducted to the sink or sinkstime-synchronously and to reproduce them there.

[0003] In case of conducting synchronous signals through asynchronoussignal paths, time-synchronous conduction to the signal sinks can beachieved by introducing time marks into the data signal to betransferred. These introduced time markers are used at the end of anasynchronous path for conducting the signals correctly in time. The timemarks are then removed again from the transferred data signal.

[0004] Known digital transfer systems are based on this principle. Inthese, by predetermining a reference model for the receiver, theoccurring delay times and processing times are known, so that the senderor the signal source can calculate the time marks to be introduced intothe data signals, using a common time basis and the known delay times orprocessing times. Systems which operate according to this procedure aredescribed, for example, in the Standard IEC 13818 “Coding of movingpictures and associated audio” as well as in IEC 61883-4 “Consumeraudio/video equipment—Digital interface—Part 4: MPEG data transmission”.

[0005] In the known procedure, it is a disadvantage that it can only beused if known signal processing paths are present, because aprerequisite is the presence of a reference model of the different datapaths with the aid of which the occurring delay times and processingtimes can be determined.

[0006] Based on this state of the art, the task of the invention is tocreate a method or a device for time-synchronous conduction of signalswhich does not have the above disadvantages.

[0007] This task is solved by a method with the characteristics given inclaim 1 and by a device with the characteristics given in claim 5.Advantageous embodiments and further developments of the inventionfollow from the dependent claims.

[0008] The advantages of the invention lie especially in the fact thattime-synchronous conduction of signals transferred through varioussignal paths, which signals are subjected in these signal paths todifferent signal-processing-related delays, is ensured even whenheterogeneous data paths are present. By determining the delays thatoccur in the various signal paths, which is preferably done individuallyfor each process step, and the subsequent calculation of a minimum totaldelay, can take place at the site of application itself, within theframework of the first start-up of an installation and/or during runningoperation, with the aid of an installation-specific calculation of theminimum total delay. This calculated value can be updated eitherautomatically at the given time intervals, automatically upon changingof the signal path or after the input of an operating command. As aresult of that, even changes in the signal path architecture can betaken into consideration, for example, with an intermediate connectionof other signal processing units or removal of signal processing unitsfrom the installation. By inserting information about the calculatedminimum total delay into the data signal to be transferred, it iscommunicated to a delay unit arranged in the signal way before thesignal sink as to which individual delay must be imposed on a signaltransferred in the particular signal path in order to achieve that thesignals transferred in all signal paths can be conductedtime-synchronously to the sink or sinks.

[0009] Application of the claimed method and of claimed device can beused not only for audio/video systems and in multichannel audio systems,but, for example, also in other consumer electronics systems, homenetwork systems and all other information transfer systems in whichsignals from at least one signal source have to be transferred throughvarious signal paths to at least one signal sink and must arrive theretime-synchronously.

[0010] The invention will be explained in more detail below with the aidof a practical example, which is represented in the figures. Thefollowing are shown:

[0011]FIG. 1 is a device for time-synchronous conduction of signals and

[0012]FIG. 2 is a corresponding delay diagram.

[0013]FIG. 1 shows a device for time-synchronous conduction of signalsoperating according to the method of the invention.

[0014] The device shown has two signal sources 1, 7, the output signalsof which must be transferred through various signal paths to signalsinks 6, 12, 17.

[0015] In the first signal path, which extends from the output of signalsource 1 to the input of signal sink 6, one behind the other, are adevice 2 for introducing time marks, a signal processing unit 3, asignal processing unit 4 and a delay unit 5.

[0016] The second signal path, which extends from the output of signalsource 7 to the input of signal sink 12, contains, in sequence, a device8 for introducing time marks, a signal processing unit 9, a signalprocessing unit 10 and a delay unit 11.

[0017] In the third signal path, which extends from the output of signalsource 7 to the input of signal sink 17, a device 8 for introducing timemarks, a signal processing unit 9, a signal processing unit 15 and adelay unit 16 are provided in sequence.

[0018] Furthermore, the device shown has a control unit 13, which ispreferably a microcomputer.

[0019] This is connected with a time base 14, which makes the controlunit available for the entire device as time base signal serving as timebase. Furthermore, the control unit 13 has one or several inputs throughwhich the maximum possible delay time of the signal processing units 3,4, 9, 10 and 15 can be queried. It is generally assumed that theindividual signal processing units determine or know the delay timethemselves. The information about a delay belonging to a signalprocessing unit can also be determined using time base informationcontained in the transferred signal, or, if a reference model ispresent, it can be known to the control unit a priori. In addition tothe time base information contained in the transferred signal, fordetermination of the delay belonging to a signal processing unit, onecan make use of delay values belonging to other signal processing units,stored in the control unit 13 previously.

[0020] For example, the time base information in signal source 1, madeavailable by signal control unit 13, can be used as the first time markin the output signal of signal source 1. The output signal of signalsource 1 first runs through device 2 and then it is subjected to asignal processing procedure in signal processing unit 3, where asignal-processing-specific delay is imposed on the signal to betransferred. This signal-processing-specific delay value can bedetermined either in the signal processing circuit 3 by evaluation ofthe time base information, then informing the control unit 13, or it canbe determined first in control unit 13 itself, which also has access tothe time base.

[0021] The determined signal-processing-specific delay value, which isassigned to signal processing unit 3, is stored in control unit 13.

[0022] The output signal of signal processing unit 3 is introduced tosignal processing unit 4 and there is subjected to anothersignal-processing-specific delay. This additionalsignal-processing-specific delay can be determined either in thesignal-processing unit 4 itself, by evaluating the time base informationand then provided to control unit 13, or it can be first determined inthe control unit 13 itself, which also has access to the time base 14and which also has information about the delay value assigned to signalprocessing unit 3.

[0023] The determined signal-processing-specific delay value, which isthe basis of signal processing unit 4, is also stored in control unit13.

[0024] By summation of the delay values assigned to signal processingunits 3 and 4, the signal-processing-related delay occurring totally inthe first signal path is determined in control unit 13, and stored asdelay value. Similarly, the delays occurring in signal processing units9 and 10 are determined and, by their summation, the total occurringdelay in the second signal path is calculated and stored as delay valuein control unit 13. Similarly, a determination of the delay occurring insignal processing unit 15 is done and by summation of the delaysassigned to signal processing units 9 and 15, the total delay occurringin the third signal path is calculated and correspondingly stored incontrol unit 13.

[0025] Then, in control unit 13, a comparison of the total delaysoccurring in the three signal paths is performed with the purpose ofdetermining a minimum total delay. The minimum total delay preferablycorresponds to the maximum value of the delays occurring in the threesignal paths, but it can also be chosen to be larger in order to have atime reservoir available.

[0026] Now, if it is ensured in each of the signal paths that theconduction of the particular signal to the corresponding signal sinktakes place only at or after the end of the minimum total delay, andthen time-synchronous conduction of the signals to signal sinks 6, 12,17 can be achieved.

[0027] In order to achieve this, control unit 13 has time informationavailable at an output which information contains the time base signaldelayed by the minimum total delay. This signal is introduced to each ofdevices 2 and 8 and there it is entered into the signal to betransferred, originating from the particular signal source.

[0028] This information, together with the signal to be transferred,passes through the particular signal path and arrives to delay units 5,11 and 16. These also have the time base signal of time base 14available. The time information in the signal shows when the particulardelay unit should further conduct the signal at the output. Thus, alwaysan individual delay of the signal to be transferred occurs with a delaytime which corresponds to the difference between the minimum total delayand the signal-processing-related delay imposed on the signal in theparticular signal way. The delay unit of each signal path is arranged inthe signal way between the signal source and the signal sink, preferablybetween the last signal processing unit of the particular signal way andthe particular signal sink.

[0029]FIG. 2 shows a delay diagram which illustrates the time course ofthe device shown in FIG. 1.

[0030] In this diagram, it is assumed that the signal sources 1 and 7make their output signals available at the same time at time point t0.This time synchronicity can be ensured by the control unit 13, whicheither starts the signal sources simultaneously, or introduces a commontime base signal into the signal sources on the basis of which thesignal sources begin with the output of the signal.

[0031] In the upper part of the diagram, the delays occurring in thefirst signal path are illustrated. Thus, τ1 designates the delay time towhich the signal to be transferred is subjected in signal processingunit 3 and τ2 designates the delay time to which the signal to betransferred in signal processing unit 4 is subjected. The symbol τ3 isthat individual delay time which corresponds to the difference betweenthe minimum total delay τ8 and the sum of the delay times τ1 and τ2, sothat:

τ3=τ8−(τ1+τ2).

[0032] The signal to be transferred in the first signal path in delayunit 5 is delayed by this individual delay time 13.

[0033] In the lower part of the diagram, the delays occurring in thesecond and third signal path are illustrated.

[0034] In the second signal path, τ4 designates the particular delaytime to which the signal to be transferred in signal processing unit 9is subjected, and τ5 designates the delay time to which the signal to betransferred in signal processing unit 10 is subjected. The symbol τ6 isthat individual delay time watch corresponds to the difference betweenthe minimum total delay τ8 and the sum of the delay times τ4 and τ5,that is:

τ6=τ8−(τ4+τ5).

[0035] The signal to be transferred in delay unit 11 is delayed by thisindividual delay time τ6 in the second signal path.

[0036] In the third signal path, τ4 designates the delay time to whichthe signal to be transferred in signal processing unit 9 is subjectedand τ7 designates the delay time to which the signal to be transferredin signal processing unit 15 is subjected. The individual delay time,which corresponds to the difference between the minimum total delay τ8and the sum of the delay times τ4 and τ7 is equal to zero in thepractical example shown here. Consequently, after passing through signalprocessing unit 15, the signal transferred in the third signal path isnot subjected to any further individual delay, since the sum of thesignal-processing-related delays occurring in the third signal pathcorresponds to the minimum determined total delay.

[0037] After passage of the minimum total delay designated with τ8, thatis, at time t1, the output signals of the three signal paths areconducted further, time-synchronously, to the particular signal sink 6,12 or 17.

[0038] According to an embodiment of the invention, which is not shownin the drawings, the minimum total delay is chosen to be greater thanthe sum of the signal-processing-related delays in the signal path thathas the longest delay in this regard, in order to have a desired timereservoir with regard to the time-synchronous conduction of the signals.In this embodiment, an individual delay of the signal to be transferredoccurs in each signal path.

[0039] Alternatively to the embodiment shown in FIG. 1, the insertion oftime marks, which contain information about the minimum total delay, canalso be done in the signal sources themselves.

[0040] Furthermore, these time marks, which contain information aboutthe minimum total delay, can also be used for modification of the firsttime marks already contained in the signal, which were alreadyintroduced in the signal source into the signal to be transferred and,for example, contain information about the common time base.

[0041] In another embodiment, which is not shown in the figures either,the information about the minimum total delay is not introduced into thesignal to be transferred, but, independently of this, is transmitted tothe particular delay unit in which the creation of the individual signaldelay occurs in order to produce time-synchronicity.

[0042] The calculation of the minimum total delay in the control unitcan be done once during the start-up of the device in an initializationrun, which is automatic or is triggered after the input of an operatingcommand, and then can also be updated during later operation. This is ofspecial importance when changes in the signal path architecture areproduced, for example, by introducing or removing components from one orseveral of the signal paths. In these cases, the minimum total delay isnewly calculated, which then will be the basis for the calculation ofthe individual delays occurring in the particular signal path. Moreover,a system according to the invention requires no reference model of thesignal processing paths, with the aid of which the occurring delays canbe measured, but it is only at the place where the system is used thatthe signal-processing-related delays occurring in the signal paths aredetermined and a calculation is carried out based on this, of anindividual delay time with which the signal present in the particularsignal path must be delayed in order to provide time-synchronousconduction of the signals transferred through the different signalpaths.

1. Method for the time-synchronous conduction of signals in whichvarious signals from at least signal source are transferred throughdifferent signal paths to at least one signal sink, where time marks areintroduced into the different signals, characterized by the fact thatthe delays occurring in the different signal paths are determined, aminimum total delay is calculated from the determined delays, which isgreater than or equal to the particular delay that occurs in the signalpath with the largest delay, the time marks inserted into the varioussignals contain information about the minimum total delay, and anindividual delay is imposed in each signal path on the signal to betransferred, corresponding to the difference between the minimum totaldelay and the signal-processing-related delay that is imposed on thesignal in the particular signal path.
 2. Method according to claim 1,characterized by the fact that the signals transferred through a signalpath are subjected to several process steps in this signal path, where adelay time is determined for each of these process steps and/or thedelay values determined in each of the process steps are introduced to acontrol unit and the control unit calculates the minimum total delayfrom the delay times entered into it.
 3. Method according to claim 2,characterized by the fact that the minimum total delay is calculatedwithin the framework of an automatically occurring initialization run orthe minimum total delay is calculated after the input of an operatingcommand.
 4. Method according to claim 3, characterized by the fact thatthe minimum total delay is calculated automatically at predeterminedtime intervals or the minimum total delay is calculated at each changeof the signal path architecture.
 5. Device for the time-synchronousconduction of signals, with at least one signal source, at least onesignal sink, and several signal paths provided between the at leastsignal source and the at least one signal sink, characterized by thefact that, furthermore, they contain means (13) for the determination ofthe delays occurring in the various signal paths, means (13) for thecalculation of a minimum total delay from the determined delays, whichminimum total delay is greater than or equal to the particular delaywhich occurs in the signal path with the largest delay, means (13) forthe control of the insertion of time marks, which contain informationabout the minimum total delay, into the different signals, and in eachsignal path there is a delay unit (5, 11, 16) in which an individualdelay is imposed on the signal transferred in the signal path, the delaycorresponding to the difference between the minimum total delay and thesignal-processing-related delay that is imposed on the signal in thissignal path.
 6. Device according to claim 5, characterized by the factthat the means for the determination of the delays occurring in thevarious signal paths, the means for calculation of the minimum totaldelay and the means for control of the insertion of the time marks are acontrol unit and/or the control unit is connected to a time base (14).7. Device according to one of claims 5 or 6, characterized by the factthat a signal-processing unit (3, 4, 9, 10, 15) is arranged in one orseveral signal paths, in which the transferred signal is subjected to asignal-processing-specific delay and/or always one or several signalprocessing units are arranged in one or several signal paths, in whichthe transferred signal is always subjected to asignal-processing-related delay and/or each signal processing unit hasan output which is connected to the input of the control unit.
 8. Deviceaccording to one of claims 5 to 7, characterized by the fact that adevice (1, 7; 2, 8) for inserting time marks is provided in each signalpath, in which device the time marks generated by the control unit (13)are introduced into the signal produced by the signal source (1, 7). 9.Device according to claim 8, characterized by the fact that the devicefor introducing time marks is the signal source (1, 7) and/or the device(2, 8) for introducing time marks is arranged in the signal way, betweenthe signal source and the signal sink, or the device (2, 8) forintroducing time marks is arranged in the signal way, between the signalsource and the first signal processing unit of this signal way. 10.Device according to claim 9, characterized by the fact that the controlunit (13) has an output at which time-base signals can be taken off,that the at least one signal source is provided for insertion of thefirst time marks derived from the time-base signals into the signaltransferred through the signal path, and that the device arranged in thesignal path between the signal source and the signal sink is providedfor introducing time marks for modification of the first time marks. 11.Device according to one of claims 5 to 10, characterized by the factthat the delay unit (5, 11, 16) of each signal path is arranged in thesignal way between the signal source (1, 7) and the signal sink (6, 12,17).
 12. Device according to claim 11, characterized by the fact thatthe delay unit (5, 11, 16) of each signal path is arranged in the signalway between the last signal processing unit (4, 10, 15) of this signalpath and the signal sink (6, 12, 17).